In 2010, Americans consumed around 30 percent of their calories from meals prepared outside the home, compared with 35 percent in 2005. And the number of meals eaten at home increased from 5.8 a week to 6.29.

These reductions "accounted for 20 percent of the improvements in diet quality," the study said.

The number of meals from outside the home began to slowly climb in 2010, the study authors noted, but they said consumers were more mindful of the food's quality.

Overall, there were "encouraging findings" that "more Americans are paying attention on nutrition facts and prioritizing nutrition in the household," said Kevin Concannon, USDA under secretary for food, nutrition and consumer services.

More than one in three adults, or 78 million Americans, is obese.

The epidemic has resulted in an increase in public and private initiatives to combat Americans' overweight lifestyles, which are blamed for an estimated $190 billion in medical spending each year.